1. Field of the Invention
This invention relates, generally, to the grafting of cells. In particular, it relates to a method of inducing epidermal growth and a device for spraying a cell suspension from a tissue sample obtained from a donor site and distributing that cell suspension to a recipient site, and its method of use thereof.
2. Brief Description of the Prior Art
Spraying of cells may be of interest for the distribution of cell suspensions onto a tissue wound. This can be applied, for example in general surgery to help regenerate tissue trauma. Methods for treating skin wounds are known. For example, skin grafting techniques exist, which aim to reconstruct skin areas of the body that have suffered either damage or defects to the skin. In general, these types of grafts are classified according to their host-donor relationship and by their thickness. The most clinically applied graft is the autologous graft, whereby tissue is taken from one area of the body and applied to another area. The grafted tissue then develops a new blood supply and attaches to the underlying tissues. There are several types of skin grafts presently used, including split-thickness, full-thickness grafts, and micro-grafting. Each of these graft types must be prepared using certain techniques, and each one has its inherent advantages and disadvantages. Split-thickness grafts often require considerable skill, time and expensive equipment. Further, donor sites are painful, result in scarring and limit the coverable area. Although split-thickness grafts may be more successful than full-thickness grafts, they are usually cosmetically less attractive. Full-thickness grafts require less skill and expensive equipment, and their cosmetic appearance is better than that of split-thickness grafts. However, full-thickness grafts do not “take” as well as split-thickness grafts. Micro-grafts are more easily accomplished and require no special instruments. However, their cosmetic appearance is not as good as other techniques, as the resulting scarring is unacceptable.
A variation to the above grafting techniques is the mesh graft, which is a type of split-thickness or full-thickness skin graft in which parallel rows of slits are cut into the treated tissue. Some of the advantages of mesh grafts include: greater coverage of the affected area, drainage of blood or serum from beneath the graft, and increased conformity of the graft to uneven recipient areas. This technique has been very successful, with 90 to 100 percent “take” after the grafts have been applied on healthy granulation beds.
An alternative to split-thickness grafting is to form a blister under suction at a donor site, then remove the skin above the blister and transplant it onto the recipient site. The production of blisters to treat wounds has been used since the 1960s. The blisters are produced by a suction device, such as DERMAVAC, at a suction pressure of approximately 250-300 mmHg for 1-2 hours. The blisters are then cut off and placed on the wound. The healing time is around 10-14 days. There are several disadvantages to this method, for example lengthy preparation of the graft and/or the graft itself potentially not resulting in re-pigmentation of the area; or the graft possibly resulting in uneven pigmentation around the edges of the area of treatment.
Micro-grafting has become a more common approach for large area cover and involves the “snipping off” of a number of very small sections of tissue from a donor site and applying them to a dressing that is in turn applied to the wound area.
Another technology for the generation of tissue in vitro is to culture epidermis. Cultured epithelial autografts (CEA), provided in confluent grown cell sheets, are an important adjunct in the coverage of burns and other situations in which large areas of the body's surface experience skin loss. There are many centers throughout the world with tissue culture facilities whose aim is to produce autologous epithelial grafts for use in a wide variety of applications. The usefulness and application of CEA is related to its ability to achieve confluent cells sheets suitable for grafting. This technique overcomes many of the disadvantages of the previous treatments described above. For example, cultured epithelial autografts reduce the demand for donor sites. However, these autografts are slow growing and require time to culture, which often exceeds the preparation time of the recipient's sites. Moreover, blister formation by wound secretion below the sheet grafts hinder grafting.
Navarro et al. (2000) and Wood et al. (2003) describe the use of single cells suspended in Hartmans's solution and distributed over the wound, thus avoiding the sheets. The cell suspension may be delivered via a pipette, common “eye-droppers,” syringe and needle, and/or other similar devices to place small quantities of cellular suspension on a graft site. As method of choice a mechanical hand driven spray technique is described (see references).
The spray technique addressed some aforementioned problems in the field. A hand driven spray method and subsequent distribution of the cells, however, is not performed in a controlled manner and thus results in uneven cell distribution
Accordingly, what is needed is an improved device and technique for skin grafting. However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the art how the limitations of the art could be overcome.
While certain aspects of conventional technologies have been discussed to facilitate disclosure of the invention. Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects discussed herein.
The present invention may address one or more of the problems and deficiencies of the prior art discussed above. However, it is contemplated that the invention may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the claimed invention should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.
In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.